1. Field of the Invention
This invention relates to improved pressure transfer units, and more particularly to an improved pressure transfer unit for separating a fluid in a conduit or vessel from another fluid which is pressurized for various purposes, say, for example, to maintain a relationship of fluid pressure in vessels or conduits, while maintaining a positive barrier between the fluids; to transmit pressure in a pressure sensing device where the fluid being sensed must be excluded from the pressure indicating means; to act as a snubber for modulating pressure surges; to feed a liquid to a system at a controlled pressure; to accumulate fluid; to translate changes in pressure into mechanical action for operating various devices such as switches, solenoids, valves, and the like; and to provide a hydraulic piston.
2. Description of Certain Prior U.S. Applications
A pressurizing and cooling system for mechanical seals is shown and described in the pending application for U.S. Pat. filed June 29, 1972, Ser. No. 267,449, by Martinez et al., for "Pressurized Cooling System for Mechanical Seals," wherein a buffer fluid is pressurized in response to the pressure of fluid in a conduit, such as a pump intake, whereby the buffer fluid is maintained at a pressure in a double mechanical seal chamber greater than the pressure in the pump housing. The pressurizing systems disclosed in the Martinez et al. application employ pressure transfer units having elastomeric diaphragm assemblies. However, such diaphragm assemblies are not universally applicable due to the tendency of certain fluids to attack and/or penetrate the elastomeric material.
Another pressure transfer unit is shown and described in the application for U.S. Pat. filed Aug. 7, 1972, Ser. No. 278,475, by Charles H. Diehl. This pressure transfer unit also employs an elastomeric diaphragm assembly, and also is not universally applicable.
Still another pressure transfer unit is shown and described in the application for U.S. Pat. filed Sept. 7, 1972, Ser. No. 287,166, by Lee Joe Alley. This pressure transfer unit employs a pressure transferring separator having a metallic bellows. However, this unit has no means for limiting the quantity of fluid that can be pumped into it, and hence the bellows and other of its parts can be subjected to unduly high fluid pressures that may damage the bellows and other components of the unit. In order to partially meet this difficulty, the bellows should be especially rugged and strong to withstand any inadvertently applied excessive fluid pressures.